Crystallographic Insights into the Behavior of Highly Acidic Metal Cations in Ionic Liquids from Reactions of Titanium Tetrachloride with [1-Butyl-3-Methylimidazolium][X] Ionic Liquids (X = Chloride, Bromide, Tetrafluoroborate)

Abstract

Highly charged metal ions are difficult to investigate in weakly coordinating ionic liquids (ILs) because of the insolubility of their solid forms, but the molecular liquid TiCl4 offers a way to react tetravalent metal ions in an IL. Reactions of TiCl4 with 1-butyl-3-methylimidazolium ([C4mim] +)-based ILs containing chloride or bromide lead to mixtures of highly metastable amorphous solids and small amounts of crystalline chlorotitanate salts including [C4mim]2[TiCl6] and two polymorphs of [C4mim]2[Ti2Cl10] in a manner not well correlated with stoichiometry or anion identity. The reaction of TiCl4 with [C4mim][BF4] yields crystals of the mixed fluoro-chloro complex [C4mim]2[Ti4F6Cl12], indicating spontaneous reaction of the IL ions to generate HF in situ. These unusual behaviors are explained in terms of the exceptionally high acidity of Ti 4+ and the unusual behavior of TiCl4 among metal halides as a nonpolar molecular compound.

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

“… 376 Another formal, but this time complete, exchange of the terminal fluorine atoms by chlorine was observed for [C 4 mim] 2 [(TiCl 3 ) 4 F 6 ] (687, C 4 mim = 1-butyl-3-methylimidazolium) obtained after an ionothermal reaction of TiCl 4 under decomposition of the [BF 4 ] counterion of the ionic liquid. 377 …”

Crystal and magnetic structure of the (trimim)[FeBr4] molten salt: A temperature dependence study

“…These transitions, which are usually produced by the dynamical reorientation of their organic alkyl moieties, lead to a wide range of interesting features that can be tuned through temperature or other external stimuli like pressure or electric fields. [8,9,[11][12][13][14][15] In this contribution, we expand our previous research on imidazolium-based tetrahaloferrate(III) compounds by the temperature analysis of a newly synthesized molten salt containing the 1,2,3-trimethylimidazolium cation and tetrabromoferrate anion, (trimim)[FeBr4] (1). The interest on this family arose from the combination of imidazolium-based molecules with tetrahaloferrate anions, which are responsible for solid-to-solid phase transitions induced by the thermal treatment and long-range magnetic ordering at low temperature.…”